The present invention relates generally to a gas turbine engine reduction gearbox, and in particular, to an integrated roller bearing and oil transfer sleeve for use in a gas turbine engine reduction gearbox.
Reduction gearboxes of gas turbine engines, especially those in acrobatic propeller-driven engines, experience considerable in-flight stresses resulting in significant bending of all rotating shafts within the gearbox. As these gearboxes contain gears rotating at extremely high speeds, a constant supply of oil is required for cooling and lubrication of the components. As such, it is known to feed oil to rotating gears via paths between concentric rotating parts and internal oil supply cavities within the shafts and planetary gear carriers. These oil paths and cavities can become restricted due to the flight stress-induced bending of the components, which results in a reduced oil flow to the rotating elements.
It is currently known to use an oil transfer sleeve 52 which aids distribution of oil within a gearbox 50, as shown in FIG. 1. Such a sleeve 52 generally receives oil from an outer chamber 54, and provides distribution of the oil to inner rotating elements such as the planetary carrier 56 and the planet gears 58. An oil film can be provided within the inner diameter of the oil transfer sleeve 52, creating a journal bearing for supporting the inner rotating shaft 60 of the planetary carrier 56, for example. Internal oil feed cavities 62 within the inner shaft 60 that is supported by the journal bearing can become pinched by bending forces, resulting in reduced oil flow to the rotating gears.
There is therefore a need for a new shaft supporting member which reduces shaft bending and provides oil to the shaft inner cavities.
It is an object of the present invention to provide a bearing element which reduces shaft bending in a gas turbine engine gearbox.
It is a further object of the present invention to provide a roller bearing assembly integrally formed with a fluid transfer sleeve capable of lubrication fluid distribution.
Therefore, in accordance with the present invention, there is provided an integrated roller bearing and fluid transfer sleeve adapted for supporting and transferring fluid to a rotating shaft in a gas turbine engine reduction gearbox, the integrated roller bearing and fluid transfer sleeve comprising: a fluid transfer sleeve comprising a sleeve casing defining therein an annular fluid plenum open radially outwardly; at least two spaced apart roller bearing assemblies each comprising an annular outer race integral with the sleeve casing and each assembly including a plurality of roller elements supported by said outer race, each roller bearing assembly being disposed within the sleeve casing, one at each opposing end thereof, and the plurality of roller elements in each assembly defining a first inner diameter substantially equal to an outer diameter of the rotating shaft adapted to be supported by the roller bearing assemblies; the sleeve casing having an inner circumferential, axially extending surface, between said roller bearing assemblies, and defining a second inner diameter greater than said first inner diameter, such that an annular fluid leakage clearance can be formed between said inner circumferential surface of the sleeve casing and an outer circumferential surface of the rotating shaft; and at least an aperture being defined in the sleeve casing, permitting fluid flow from the annular fluid plenum to the fluid leakage clearance; whereby fluid in the fluid leakage clearance is transferable to the roller elements of the roller bearing assemblies and to the rotating shaft.
There is also provided, in accordance with the present invention, a composite bearing assembly adapted for supporting a rotating shaft in a gas turbine engine reduction gearbox, the composite bearing assembly comprising: a substantially cylindrical sleeve casing having at least a roller bearing disposed at each end thereof; the roller bearing comprising an outer race, integrally formed with the sleeve casing, and a plurality of roller elements supported by the outer race and disposed radially inward therefrom; and the sleeve casing comprising a central portion, axially located between the roller bearings, comprising an inner circumferential surface having an internal diameter greater than an outer diameter of the rotating shaft adapted to be supported by the roller bearings, such that an annular fluid leakage clearance, adapted to receive a fluid therein, is formed between said inner circumferential surface and an outer surface of the rotating shaft; whereby the composite bearing assembly provides both direct rolling contact and hydrodynamic support for the rotating shaft.